One of the critiques of Google Apps was its approach to service level agreements. Specifically, downtime of less than 10 minutes wasn't included as part of the SLA. Google has amended its SLA so that even shorter amounts of downtime are now is included.

Moreover, Google has removed an SLA provision that permitted scheduled downtime. "Going forward, all downtime will be counted and applied towards the customer's SLA," wrote Matthew Glotzbach, Google's enterprise product management director, in a blog post last month announcing the new policy.

Despite some outages, Glotzbach said that Gmail was available 99.984 percent of the time last year, covering both business users and consumers. "People expect e-mail to be as reliable as their phone's dial tone, and our goal is to deliver that kind of always-on availability with our applications," he noted.

As Google and Microsoft argue over whose service has features more conducive to how information is created and shared, availability and meeting service requirements will remain high on the requirements list. Providing E-mail dial tone must be a given. Google and Microsoft both appear to get that but the proof will be whether they can deliver.